The effect of sampling protocol on spatial patterns in marine bivalve diversity along the eastern coast of India

ABSTRACT Marine molluscan diversity is highly heterogeneous both spatially and latitudinally. Several hypotheses, including biotic and abiotic ones, have been put forward to explain these diversity distribution patterns across space and latitude, although sampling protocol can detrend any existing pattern. To highlight the role of sampling protocol, the present study analyses the spatio-latitudinal diversity patterns in marine bivalve dead assemblages along the eastern Indian coast, covering c. 15° latitudinal bins, using three types of datasets based on three different sampling protocols: monograph data from the published literature, bulk sampling and random sampling. In terms of composition, both random and bulk samples indicate similar species abundance distribution patterns in almost all locations, although different evenness patterns emerge for these sampling protocols. Diversity shows variable spatio-latitudinal trajectories for the three sampling strategies. For bulk samples, the low-latitude ecoregions show relatively higher diversity than the higher-latitude ecoregions, although no such patterns emerge from the random and monograph samples. Moreover, diversity peaks are located at different latitudes for the different sampling strategies. Our results highlight that the very different spatial and latitudinal patterns in diversity can be achieved through different sampling protocols, suggesting its role in influencing large-scale spatial patterns in diversity.